Center opening elevator door systems consist of a pair of car doors and a pair of hoistway doors. Each pair of doors open and close about a central point in an elevator doorway.
Linkages are used to open and close center opening elevator door systems. A door operating unit attaches to each car door via the linkage. Due to the arrangement of the linkages relative to the door operating unit and each door, it is known that one car door will move at a varying speeds relative to the other car door.
In a typical linkage driven elevator door system, a single vane is disposed between a first car door and a first hoistway door. As the car doors opens or closes, driven by the linkages, the first hoistway door opens or closes with the first car door due to the connection via the vane.
The two hoistway doors are fixedly connected by a cord (known in the art as an air cord) disposed about a pair of pulleys. As the first hoistway door opens or closes, the second hoistway door also opens or closes due to its connection via the air cord. Because the hoistway doors are connected via the air cord, they travel at the same speed as each other. The hoistway doors also travel at the same speed as the first car door due to their attachment to the vane. However, the second car door travels at a different speed than the first car door and the hoistway doors.
Because the hoistway doors are fixedly connected by the air cord, a single door lock may be utilized. By locking one hoistway door, the other door is necessarily locked due to its attachment via the air cord.
It is desirable to utilize a two vane system in high performance door systems. A two vane system couples each car door to a respective hoistway door by means of a vane. This type of system is shown in Voser U.S. Pat. No. 3,783,977 which shows a linkage that utilizes two vanes. Such a system allows the hoistway door and car door open and close in register in a smooth manner. However, a separate door lock for each hoistway door is required. Two door locks are undesirable because of electrical and maintenance requirements, complexity, and cost.